Separation of columbium and tantalum



Patented Sept. 13, 1949 SEPARATION OF COLUJMBIUM AND TAN TALUM Robert M.Fowler, Niagara Falls, N. Y., assignor, by mesne assignments, to UnionCarbide and Carbon Corporation, a corporation of New York No Drawing.Application February 21, 1946, Serial No. 649,397

3 Claims. 1

The invention relates to the treatment of ores containing columbium andtantalum, and more particularly to the separation and recovery ofcolumbium and tantalum compounds from such ores.

- Columbium and tantalum ordinarily occur in nature as isomorphousmixtures of the pentoxides of the metals and it is extremely exceptionalto find one without a considerable proportion of the other. When thetantalum pentoXide content is higher than the columbium pentoxide, theore is called tantalite; similarly when the columbium pentoxide contentis higher, the ore is called columbite.

Both columbium and tantalum have a fairly wide commercial usage and arebecoming increasingly important in the field of stainless and heatresisting alloys. The invariable occurrence of these two metalstogether, the similarity of their compounds, and the diificultyexperienced in separating them from each other and from associatedmetals have been retarding factors to their more general usage.

It is an object of this invention to provide a method of treatingcolumbite, tantalite, and similar ores to separate and recover compoundsof columbium and tantalum, each being substantially free from the other.

Another object is to prepare mixed oxides of columbium and tantalum withsubstantial freedom from other associated metal in the ore.

A further object is to prepare and separate columbium and tantalumcompounds from mixed oxides of columbium and tantalum.

According to the invention, columbium-tantalum bearing ore is treated bya method comprising digesting roasted, comminuted ore with sulfuric acidand a sulfate salt; leaching the resulting mass with water to removeacid and soluble salts; adding the residue containing columbium andtantalum to a solution of oxalic acid and an alkali metal oxalate;adjusting the pH to 2.0 to 3.0 by adding an acid, e. g. hydrochloric;adding a hydrolyzing agent (a weak base that will not produce aninsoluble precipitate of columbium at pH less than 5.0) andprecipitating the tantalum by permitting the solution to stand until thepH rises to 4.5 to 5.0; filtering out the precipitated tantalum;precipitating columbium from the filtrate by a suitable reagent, e. g.ammonium hydroxide.

In the preferred form of the invention columbium-tantalum ore, forexample, columbite or tantalite, or other ore of similar character, isgiven an oxidizing roast at 600-800 C. to render it more readilydigestable in subsequent acid treatment. The ore is preferablycomminuted to a fineness to pass through a 200 mesh screen (0.0029 in.openings) and digested for about 5 to 10 hours with acid to convert theiron and manganese to soluble salts. The digestion is preferably done ata somewhat elevated temperature in the range of 200 to 400 C. withsulfuric acid and a sulfate salt such as, for example, ammonium orsodium sulfate. The digested, pasty mass is then leached withwatenfiltered and Washed to eliminate the sulfuric acid and solublesalts, leaving the columbium and tantalum in the residue as hydratedoxides.

The residue containing the columbium and tantalum is added to a solutionof oxalic acid and potassium oxalate. The quantity of oxalic acidoxalatesolution should preferably be in slight excess over that requiredstoichiometrically to form the oxalates of columbium and tantalum. Thestrength of the solution, 1. e. the volume, appears to be of nosignificance. The presence of an alkali metal ion, preferably potassium,is essential in the subsequent hydrolysis; This indicates the formationof a soluble, duplex, potassium-columbium salt; Whereas tantalum doesnot form a similar compound under these conditions. Sodium may besubstituted for potassium in the oxalic acid solution but the resultingduplex sodium-columbium salt is much less soluble than the correspondingpotassium-columbium salt, thereby lowering the efficiency of thesubsequent separation. The pH of the resulting oxalic acidoxalatesolution is adjusted to between 2.0 and 3.0 by the slow addition of anacid, for example, hydrochloric acid.

A weak base that will not produce an insoluble precipitate of columbiumat pH less than 5.0, herein called a hydrolyzing agent, is then added.Weak bases suitable for this purpose comprise:

(a) Ammonium hydroxide.

(b) Ammonum salts of weak acids, e. g. am-

monium carbonate.

(0) Amines that yield ammonia upon hydrolysis,

e. g. urea.

(d) Alkali salts of weak acids, e. g. potassium bicarbonate.

Subsequent to this addition the reacting materials are permitted tostand under conditions favorable for hydrolysis, preferably at aslightly elevated temperature. With urea it was found that standing at atemperature of to C. gave satisfactory results. During hydrolysis the pHvalue rises. At a pH value of 4.5 to 5.0 the tantalum is substantiallycompletely precipitated, a

relatively free from columbium. The pH value should not be allowed toexceed 5.0 as columbium may be precipitated at pH values higher than5.0. Obtaining a pH value of 4.5 to 5.0, rather than a specific =time ortemper-ature is the criterion for determining thefles'i-rediend'pdintdfthe reaction.

Although a specific example has beengive'n in the foregoingspecification, this example is given At a pH value of 4.5 to 5.0 thetantalum precipitate is filtered out of the solution containing the soluble columbium salt. The columbium may borecovered from the filtrate bywell known 'prlocedures, for example, precipitation with ammoniumhydroxide. For economic reasons, it may be desirable to recover theoxalicacid from the :filtiate. This may be done byconventional-processes:such as precipitation with calcium salts andregeneration with sulfuric acid The mechanism of the reactionhereinbe'fore strued as effecting any limitation'on the scope of theinvention but is {given only :to aid in a general understandingkof theprobable operation of the inventio'n.

As a :specific example; the application of the invention to theseparation of :columbium and tantalum from columbite ore will be given.A comminuted ore containing 542% CD205 and 19.9% TazOs together withusual ore impurities including iron and manganese was roasted for 2 to'3 hours until the ore-changed in color from black to brown. -A'=chargeof 50 parts by weight of the roasted ore was digested for about 8 hoursj :at betwe'en 200 and 400 C. with 134:.1331'5S0f10011- centrate'dsulfuric'acid and 25 :parts of ammonium sulfate; 500:partsof'water wereadded'toathe pasty In'ass which'was stirred toeffect suspensionoflthesolids. 'Thesuspension was added to 4000 :parts of water, heated'atabout90" C., with contin-uous parts o'furea were added and the'solution'heated at about 90'C. unti1:the:pH1reached 48. The precipitate was thenremoved by:filtration and ignited to TazOt. The filtrate was boile'd todecompose urea afterwhicheoparts of'ammonium hydroxide were addedtoprecipitate columbium. The columbium precipitate w'as filtered out ofthe solution,

washed-and ignited to -Cb205.

About '71 of the columbium in the ore was recovered as high purityproduct'containing 93.17

'CbOaand only 1.3% TazOa. 'The tantalum precipitate obtained from thehydrolysis step containssome columbium'and much'higher yields ofcolumbium may be obtained by recycling the tantalum *from this step. Inan operation in which this was done the recovery of high purity Cb205WES 95%.

merely to illustrate the principles of the invention and a mode ofoperation. The invention is not to be limited to or by such example.

Whatisclaimed isz 1 j 1 f 1- .A unethoii or treating acre containingcolumbiuin and tantalum values comprising digesting the ore withconcentrated sulfuric acid and a sulfate salt; adding water to theproducts of the digestion; separating the water soluble and waterinsoluble products of the digestion; treating the waterinsoluble-products containing columbium rand tantalum values with oxalicacid solution contain'ing anialkaii imetal ion to effect solution ofthewater insoluble products; adjusting the pH oi the solutiontliusobtained to between 2 and 3 by the addition of an acid; adding a weakbase that will not produce an insoluble precipitate of columbium at pHless than 5.0; permitting the il-T 5 betwe n -5 and 530m pr ipita ta a uva u s "and sep ratin the p ec p a ed a a m-v lue from-the so ut na A:method-oompfiising adding oxalic acid lution containing an alkali metalion to a tureof the :oxidesof-columbiumqandtantalum to effect solutionofsuoh mixture; (adjusting the 2111-1 of such solution to ibetween 2 and3-day the addition of :an acid; adding :aweak base-twat will not,produce an insolublev precipitate-of columbium :at,

pH less than 5;!) toisuch solutioniandi permitting the pL-Ltorisetodoetween ifiriandfiiflito precipitate tantalum values :andseparating the precipitated tantalum values from the solutionQ 3.:method'of ltreating toretnnntaining columbium rand tantalum l-valuesc'omprising digesting roasted lcomminuteii ore wiithconnentratedssulfurie [acid 'and' a sulfate fsa'l t forz'irto liloincurs at a temperature rbetween i201T -1CJand soo -c; adding water tothe tproduets-xofrdigestion; filtei ini; out the insolublelresiduexcontaining the dolumbiuin "and tantammivaiues; 'ti eating 'theresidue with oxalic acid solution-boiitairiingea potassium ionto'efi'ect solutionmf the colum'bium' and tantalum values; :adjusting thep11 or the solution to betweeniand ifby the aildition-oihydrochloricacid; :adding a weak base that will not produce an insoluble precipitateo'ficolum'bium at-pI-Lless than 5.6; heating th'e 'seliition at aboutill to 100" C. unt'il the pH reaches 4 5 to to precipitatetantalumvalues and-"separating the precipitated tantalum values "fromNumber j "Name ,Date

2259,1396 "secnieeht'etial. Oct. 14, '1941 OTHER REFERENCES Powelletafi, "I'h e 'Anaiy'stifwolfio r1925) pp.

*Rohmer, icneniieai n stra tsr'v as, 11942) Certificate of Correctiontified that error quir'mg eorree 54, for the num It is hereby cernumbered patent re Column 3, line and that the said Letter nform to therecord of ame may .00

Signed and sealed this s Patent should be rea ROBERT M FOWLER printeappears in the t10n as follows:

eral 48 read 4.8;

the case 111 17th day of January, A. D.

THOMAS Assistant 00 d with this corree the Patent Offiee.

September 13, 1949 d specification of the above tion therein that the F.MURPHY,

mmissz'oner of Patents.

